Re: Differences between ULRs and SDRs


--- In ultralightdx@..., Rick Robinson <w4dst@...> wrote:
A true SDR, see the Elektor SDR receiver or RFSpace receivers, have no
RF components other than front end bandpass filters. All the functions
of the Si4734 hardware are done in software with an SDR design. An SDR
relies on the sound card of a computer along with special software to
perform all the functions the Si4734 receivers perform with hardware.
The DSP functions of the ULRs are performed with hardware designed into
the IC while the DSP of an SDR is performed by the control software.
This is kind of a narrow interpretation of SDR. One realization of SDR is, as you say, some minimal hardware feeding a PC with soundcard, followed by further digital signal processing via a program in the PC. But the Si4734 internally does all the same steps, including an initial RF front end and downconversion to I/Q ADCs. All further filtering, demodulation, signal processing, and audio processing are done by an embedded, programmable DSP engine in concert with an embedded programmable microcontroller. Beyond the initial downconversion circuits, there is no difference in hardware between the AM/FM/SW/WB processing other than embedded firmware.

There is no way for a customer to adapt the Si4734 for SSB demodulation, but there is no technical reason Silicon Labs could not program the capability. The main impediment is that market demand for SSB is very small compared to other opportunities.


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